Wiper blade assemblies

ABSTRACT

The invention seeks to provide an improved wiper blade assembly, and in a broad aspect provides a windscreen wiper blade assembly comprising at least a primary yoke and a pair of secondary yokes articulated thereto, the primary yoke and/or the secondary yokes being provided with at least one wind-deflecting surface, oriented in relation to the direction of motion of the vehicle so that when said vehicle is moving to create air flow over the windscreen, air is deflected by said surface or surfaces to produce a force tending to urge the wiper blade assembly towards the windscreen of the vehicle. Two posts are provided which depend from an underside of the primary yoke to limit pivotal movement of the secondary yokes.

This is a Continuation-In-Part of Ser. No. 08/502,293 filed Jul. 13,1995 now U.S. Pat. No. 5,666,687.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wiper blade assemblies typically of thetype used for mounting windscreen wipers on motor vehicles.

2. Description of the Prior Art

A conventional single blade wiper assembly comprises a primary yoke forattachment to a wiper arm, two secondary yokes pivotally attached toopposite ends of the primary yoke, and a separate tertiary yokepivotally attached to one, usually the outermost one, of the two freeends of each secondary yoke. Claws for mounting a wiper blade areprovided at the ends of the tertiary yokes, and at the ends of thesecondary yokes not occupied by the tertiary blades. There is thusprovided a flexible six point mounting for the wiper blade, whichaffords a reasonable degree of contact between the wiper blade and thewindscreen, at least in calm conditions when the vehicle is stationaryor travelling at comparatively slow speed.

Dual wiper blade assemblies are also know for mounting a pair of wiperblades. Typically a known dual wiper blade assembly comprises a primaryyoke, one or two secondary yokes pivotally attached to each end of theprimary yoke and a separate tertiary yoke articulated to one of the twoends of each secondary yoke. The free ends of each of the secondary andtertiary yokes are provided with claws for mounting a pair of generallyparallel wiper blades.

A problem arises with known wiper blade assemblies, however, when thevehicle is travelling forwards, creating an upward and transverse airflow over the windscreen. The wiper blade assembly naturally tends tolift away from the windscreen on its downward stroke as air flowintervenes between the windscreen and the wiper. When the vehicle istravelling at speed, the problem is exacerbated.

SUMMARY OF THE INVENTION

The invention seeks to provide an improved wiper blade assembly, and ina broad aspect provides a windscreen wiper blade assembly comprising atleast a primary yoke and a pair of secondary yokes articulated thereto,the primary yoke and/or the secondary yokes being provided with at leastone wind-deflecting surface, oriented in relation to the direction ofmotion of the vehicle so that when said vehicle is moving to create airflow over the windscreen, air is deflected by said surface or surfacesto produce a force tending to urge the wiper blade assembly towards thewindscreen of the vehicle.

As mentioned above, the principal problem with wind-lift of the wiperblade from the windscreen occurs primarily on the downward stroke of thewiper. Therefore each deflector surface may therefore consist of orinclude a surface element which slopes downwardly towards (i.e. is notperpendicular to) the windscreen of the vehicle, when the wiper bladeassembly is mounted thereon in a generally horizontal position. This maybe accomplished by either a curved or a flat surface, as will beexplained more fully below.

In some preferred embodiments, deflection surfaces are provided bycurved portions of the outer profile of the assembly. For example, ahollowed out or indented portion may be provided on the outer surface ofthe assembly (i.e. the surface facing in the direction of motion of thevehicle). Preferably the conformation of the hollowed out portion iseffective to deflect air from a path generally perpendicular to theouter surface of the assembly (which will be the predominant directionof incidence of air flowing over the windscreen during forward movementof the vehicle) to a direction generally parallel to said outer surface.By such means, a major part (and preferably substantially the whole) ofthe momentum of the air flow incident upon the deflection surface istransferred to the wiper blade assembly, thus maximizing the biasingforce on the assembly towards the windscreen.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is hereinafter described by way of example only, withreference to the accompanying drawings in which:

FIG. 1, is a perspective view of an embodiment of wiper blade assemblyaccording to the invention;

FIG. 2, is a side elevation of the FIG. 1 embodiment;

FIG. 3, is a top plan of the FIG. 1 embodiment;

FIG. 4, is an exploded view of the components of the FIG. 1 embodiment;

FIG. 5, is an enlarged perspective view of a portion of the FIG. 1embodiment, in the vicinity of a mounting of a secondary yoke to theprimary yoke; and

FIG. 6, is a sectional view along line 6--6 of FIG. 3.

FIG. 7, is a side elevation view of an alternate embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In a specific embodiment described in detail below, the hollowed outportion intersects the outer surface of the assembly at a generallyarcuate or parabolic rim, and is formed by walls which descendrelatively steeply from the central portion of the rim, and becomeprogressively shallower away from the central portion, and towards theend portions of the rim. In the described embodiment, there are twohollowed out portions, one disposed on each secondary yoke at thevicinity at which the secondary yoke is articulated to the primary yoke,and oriented inwardly towards a central portion of the primary yoke sothat incident air is deflected generally in that direction. The hollowedout portions could alternatively, or additionally, be positioned on theprimary yoke, preferably in the vicinity of the secondary yoke mounting.An advantage of such positioning is that even pressure is applied to thelimbs of the secondary yokes. To assist further in evenly distributingthe biasing force and improving the conformability of the wiper bladewith the windscreen, tertiary yokes are articulated to the inner limbsof the secondary yokes, rather than the outer limbs.

Alternatively or additionally, deflecting surface(s) may be provided byone or more elongate members or wings extending generally parallel tothe main axis of the wiper blade assembly. Preferably, four such wingsare provided in total, arranged in two pairs, one pair being associatedwith each limb of the primary yoke. Each such pair comprises individualwings disposed substantially parallel to each other on opposite lateralsides of the limb. Conveniently, the wings are mounted on the secondaryyokes, and arranged to lie alongside the primary yoke when the secondaryyokes are mounted thereto. The deflection surfaces of the wings may beplanar or curved, but in either event are preferably oriented inwardlytowards the central axis of the primary yoke.

In another alternative arrangement, a deflection surface is provided bya side wall of a slot passing through the primary yoke, the slotproviding a through passage for air, oriented generally in the directionof travel of the vehicle. A deflection surface is provided by the slotwall positioned on the upper side of the slot, when the wiper assemblyis mounted to the vehicle in a generally horizontal parked position.Such a side wall in inclined with respect to an axis perpendicular tothe outer surface of the primary yoke, so as to slope downwardly in adirection towards the windscreen of the vehicle. The lower wall of theslot may extend generally parallel to an axis perpendicular to the outersurface of the primary yoke, or may be inclined thereto in a directionopposite to the inclination of the upper wall. It is preferred thatthere by some degree of inclination of the lower wall, but that thisshould usually be less than the degree of inclination of the upper wall.The slot is therefore tapered from the outer surface of the primary yoketowards the inner surface. A plurality of similar slots may be provided,preferably in the primary yoke, but optionally also (or alternatively)in the secondary yokes. When the slots are provided in conjunction withwings, the wings may be disposed so as to channel air into the slots.

The above described features can be used individually or in combination.In each case one or more surfaces are provided which slope downwardlytowards the windscreen of the vehicle. By this means, air flowing over awindscreen impinges on the deflection surface and produces a reactionforce directed generally upwardly towards the windscreen. During thedownward stroke of the wiper, the downward force provided by the drivingmotor counteracts the upward component of the reaction force, and thewiper assembly is forced downwards while being biased towards thewindscreen to discourage or prevent wind lift.

It will be noted in the arrangements described above which have inwardlydirected hollowed out portions, symmetrical arrangements of wings, orslots having inclined bottom walls, that in addition to the describeddeflection surfaces which slope downwardly towards the windscreen,surfaces are also provided which slope upwardly towards the windscreen.Such surfaces help to bias the wiper assembly towards the windscreenduring the upward stroke of the wiper, and are also of use in wiperswhich describe a full semi-circular path, half of which involves adownstroke with the assembly effectively inverted.

FIG. 1 shows an embodiment of wiper blade assembly of the double bladetype, but the principles of the invention are also applicable toassemblies carrying a single blade. The FIG. 1 apparatus comprises aprimary yoke 6, to which are attached two secondary yokes 7 by pivotalattachment means 62/75. Tertiary yokes 8 are pivotally mounted on theinner arm of yokes 7 by pivotal attachment means 76/83. Each yokeelement includes co-extensive longitudinal elements 9 connected one tothe other by transverse web elements 10. Wiper blades 5 comprising wiperrubbers received in backing strips are held by claws 71 and 81 providedrespectively on the secondary and tertiary yokes.

As will be seen more clearly from FIG. 5, the secondary yokes 7 areprovided with hollowed out or indented portions 73 defined by theelements 9 and webs 10, which serve to deflect impinging air in thedirection shown by the arrows in FIG. 5 and FIG. 2, when the wiper bladeassembly is placed in a head wind, for example created by the forwardmovement of the vehicle. When the wiper blade assembly is in motion in adownward stroke, the upper wall of the hollowed out portion 73constitutes a deflection surface for impinging air, which produces areaction force in the wiper blade assembly, tending to bias it towardsthe windscreen.

The secondary yokes 7 are also provided with elongate wings 74 whichextend towards the central portion of the primary yoke 6 from a positionin the general vicinity of the point of mounting of secondary yokes 7 toprimary yoke 6. Wings 74 provide deflection surfaces which slopeinwardly in a direction towards the windscreen of the vehicle. The wingsillustrated have curved surfaces, but the surfaces could equally well beflat. When the wiper blade assembly is in motion in a downward stroke,the upper wings present faces which slope generally downwardly towardsthe windscreen, and which when impinged upon by oncoming air tend toproduce a force biasing the wiper blade assembly towards the windscreen.In an alternative embodiment, the wings slope outwardly away from theprimary yoke 6 instead of sloping inwardly towards the primary yoke.

At least one post 63 (preferably two posts) depend from the underside ofthe primary yoke 6 in a position near the wings 74 on the side overwhich the wiper arm extends. The wiper blade assembly is preferably madefrom plastic materials having a degree of resilience so that the wiperrubbers conform top the shape of the windscreen under the action of thisarm. The post(s) 63 abut the upper surface of the secondary yoke 7 andprevent the tips of the wings 74 from rising too high above the primaryyoke 6 and interfering with the wiper arm, as might otherwise occurduring flexing of the wiper blade assembly. In one embodiment two postsare positioned proximate to a single one of the two secondary yokes 7.In another embodiment, one post is positioned proximate to each of thetwo secondary yokes 7.

Primary yoke 6 is also provided with slots 61 defined by elements 9 andwebs 10, which provide through passages for air to the secondary yokehollowed out portions. The inner profile of a typical slot 61 is shownin FIG. 6, from which it will be seen that the right hand wall asillustrated (which constitutes the uppermost wall of the slot when thewiper blade assembly is mounted on a vehicle in a parked condition) isinclined to an axis perpendicular to the outer surface of the wiperblade assembly, so that it presents a face which slopes downwardlytowards the windscreen. The left hand wall of the slot (whichconstitutes the lowermost wall when the wiper blade assembly is parked)is also inclined to the aforesaid axis, in the opposite direction to theright hand wall, and to a lesser extent. When the wiper blade assemblyis in motion in a downward stroke, air from a headwind enters slots 61and impinges upon the uppermost walls thereof, producing a reactionforce tending to bias the wiper blade assembly towards the windscreen.

The effect of the invention is enhanced in the illustrated embodiment bythe provision of fins 72, which also serve to create the biasing forcetowards the windscreen when the vehicle is in motion.

While the foregoing invention has been shown and described withreference to a preferred embodiment, it will be understood by thosepossessing skill in the art that various changes and modifications maybe made without departing from the spirit and scope of the invention.

I claim:
 1. A superstructure for a wiper element, comprising:a primaryyoke structure including a first pair of co-extensive longitudinalelements which are connected one to the other by first transverse webelements, each end of said primary yoke including connection means toconnect said primary yoke structure in pivotal relation to a pair ofsecondary yoke structures, said first co-extensive elements and firsttransverse web elements defining therebetween first hollowed outportions for directing airflow through said structure, said primary yokehaving at least one post depending from and substantially orthogonal toan underside thereof, said post projecting beyond a lowermost portion ofsaid primary yoke adjacent thereto and having a free end against whichone of the secondary yoke structures engages to define a positive stop,thereby limiting pivotal movement of said one of said secondary yokestructures relative to said primary yoke structure.
 2. A superstructureas recited in claim 1, wherein said at least one post comprises:twoposts depending from an underside of said primary yoke, at least one ofsaid posts being disposed proximate to each of said secondary yokestructures to thereby limit pivotal movement of said pair of secondaryyoke structures.
 3. A superstructure for a wiper element, comprising:aprimary yoke structure including a first pair of co-extensivelongitudinal elements which are connected one to the other by firsttransverse web elements, each end of said primary yoke includingconnection means to connect said primary yoke structure in pivotalrelation to a pair of secondary yoke structures, said first co-extensiveelements and first transverse web elements defining therebetween firsthollowed out portions for directing airflow through said structure, saidprimary yoke having at least one post depending from an undersidethereof to limit pivotal movement of one of said secondary yokestructures, wherein:said first hollowed out portions have aprogressively deepening depth through said structure from eachrespective end of said primary yoke to a central portion of said primaryyoke structure, said pair of secondary yoke structures each including apair of second co-extensive longitudinal elements which are connectedone to the other by second transverse web elements, said pair ofsecondary yoke structures being connected to said ends of said primaryyoke at a mid-portion of said secondary yoke, at an end of saidsecondary yoke positioned nearest the central portion of said primaryyoke, said second co-extensive elements and second connecting webelements of said secondary yoke defining second hollowed out portionsfor directing airflow through said secondary yoke structure and aligningwith said first hollowed out portions in overlying portions of saidprimary yoke structure.
 4. A superstructure as recited in claim 3,further comprising:wing means for deflecting oncoming air to therebybias said wiper element toward a windscreen, said wing means beingmounted to said secondary yoke structures at a position proximate saidconnection between said primary and secondary yoke structures.
 5. Asuperstructure as recited in claim 4, further comprising:a tertiary yokeelement mounted to said end of each of said pair of secondary yokestructures located nearest a central portion of said primary yokestructure.
 6. A superstructure for a wiper element, comprising:a primaryyoke structure including a first pair of co-extensive longitudinalelements which are connected one to the other by first transverse webelements, each end of said primary yoke including connection means toconnect said primary yoke structure in pivotal relation to a pair ofsecondary yoke structures, said first co-extensive elements and firsttransverse web elements defining therebetween first hollowed outportions for directing airflow through said structure, said primary yokehaving at least one post depending from an underside thereof to limitpivotal movement of one of said secondary yoke structures, wherein:saidfirst hollowed out portions define a slot, said slot having first andsecond opposed walls positioned in the longitudinal direction of saidstructure, said first wall being inclined with respect to lineperpendicular to a top surface of said primary yoke structure, saidsecond wall being generally parallel to said line.
 7. A superstructureas recited in claim 6, wherein:the combination of said first and secondwalls defines a tapering slot which becomes narrower through the depthof said primary yoke structure.
 8. A superstructure for a wiper element,comprising:a primary yoke structure including a first pair ofco-extensive longitudinal elements which are connected one to the otherby first transverse web elements, each end of said primary yokeincluding connection means to connect said primary yoke structure inpivotal relation to a pair of secondary yoke structures, said firstco-extensive elements and first transverse web elements definingtherebetween first hollowed out portions for directing airflow throughsaid structure; each of said pair of secondary yoke structures eachincluding a pair of second co-extensive longitudinal elements which areconnected one to the other by second transverse web elements, said pairof secondary yoke structures being connected to said ends of saidprimary yoke at a mid-portion of said secondary yoke, at an end of saidsecondary yoke positioned nearest the central portion of said primaryyoke, said second co-extensive elements and second connecting webelements of said secondary yoke defining second hollowed out portionsfor directing airflow through said secondary yoke structure and aligningwith said first hollowed out portions in overlying portions of saidprimary yoke structure; wing means mounted to said secondary yokestructures at a position proximate said connection between said primaryand secondary yoke structures, said wing means being laterally disposedto and extending alongside said primary yoke structure and the alignedhollowed out portions, said wing means being shaped so as to direct airflow inwardly towards said first and second hollowed out portions; and apair of posts depending from an underside of said primary yoke one eachexclusively disposed proximate to one of said secondary yoke structuresto thereby limit pivotal movement of said secondary yoke structures.